1. Field of the Invention
The present invention relates to devices, systems, and methods for measuring thermal properties of clothing, and, more particularly, to such devices, systems, and methods for simulating a shape, size, and temperature of a human body.
2. Description of Related Art
Exposing a human being or other mammal to an extreme temperature environment, such as high heat levels, places it at risk for disorders and/or illnesses if the exposure exceeds their tolerance. The American Conference of Governmental Industrial Hygienists (ACGIH) has proposed a threshold limit value (TLV) for heat stress and strain, including safe tolerance limits for work in hot environments, which varies according to work intensity and thermal insulation of clothing. Clothing insulation is also an important factor in protection against cold. In addition, other thermal properties of clothing such as vapor permeability and ventilation also affect human heat tolerance.
At present there are two direct methods available for the measurement of the thermal properties of clothing such as insulation and ventilation. One method requires the use of an electronically instrumented mannequin, made of metal or plastic, that is placed inside a climatically controlled chamber, the cost of which is known at present to be approximately $1 million.
A second method requires human subjects to be exposed to high heat stress conditions inside a climatic chamberwhile exercising and carrying physiological monitoring equipment, including a rectal thermometer. This approach exposes test subjects to heat stress, discomfort, and health risks. Furthermore, because of individual variability, at least 12 test subjects are needed to provide sufficient statistics for such heat stress tests.
Ventilation of garments and breathability of the garment""s material are key factors that allow metabolic heat to dissipate from a body. When garment ventilation is high, the insulation values of the protective clothing are of less significance. When the garment ventilation is low, however, the insulation value becomes very important.
Few countries around the world are believed to have laboratories where the testing of the thermal properties of protective garments can be performed using such sophisticated and expensive mannequins and instruments (Holmer and Ingar; Thermal Manikins in Research and Standards; Proceeding of the Third International Meeting of Thermal Manikin Testing, Oct. 12-13, 1999, the contents of which are incorporated herein by reference).
Among references known in the art, Green (U.S. Pat. No. 2,693,088) teaches an apparatus for conditioning compressed air to a flight suit, which regulates the circulating air to a desired temperature. The suit of Palma (U.S. Pat. No. 3,507,321) also provides temperature-regulated heating and/or cooling to all or part of a body. The space suit of Starr (U.S. Pat. No. 3,648,765) has a system for mixing warm and cold liquid to achieve temperature regulation. Chambers et al. (U.S. Pat. No. 3,736,764) disclose a fluid-cooled garment. The temperature of the coolant is based upon an evaporative water loss rate of the wearer. The hospital garment of Hardy (U.S. Pat. No. 3,738,367) has small-diameter tubes for conveying temperature-regulated fluid adjacent the body. Laxo (U.S. Pat. No. 3,743,012) teaches the use of counter-flow heat exchange to maintain an equal temperature distribution along the inner surface of a garment for use by, for example, a diver. The garment of Chuan-Chih (U.S. Pat. No. 4,747,408) provides the wearer with a portable sauna by alternately delivering hot air and cooled water to the garment. Inoshiri et al. (U.S. Pat. No. 5,805,718), in the process of determining an amount of clothing being worn by a subject, calculate the heat discharged out of the clothing and the thermal resistance of the clothing.
It is therefore an object of the present invention to provide a device, system, and method for measuring the thermal properties of clothing.
It is an additional object to provide such an invention that is significantly less costly than previous devices and systems.
It is a further object to provide such an invention that simulates a plurality of properties of a mammalian body.
It is another object to provide a system and method for measuring clothing insulation.
It is yet an additional object to provide such a system and method for measuring vapor permeability of a garment.
It is yet a further object to provide such a system and method for measuring the ventilation of the garment and the breathability of a garment""s material.
It is yet another object to provide a device, system, and method for improving the safety of mammals exposed to high temperatures.
A specific object is to provide such an invention for improving worker safety in high-temperature environments.
These objects and others are attained by the present invention, one aspect of which comprises a device for measuring a thermal property of a garment. The device comprises a mannequin having a form similar to at least a portion of a mammalian body. The mannequin is adapted to wear a garment for which it is desired to have a thermal property measured.
The device further comprises fluid circulating means for receiving a fluid therethrough having an inlet and an outlet. The fluid circulating means is positioned to travel through at least a portion of the mannequin. Means for sensing a temperature and for maintaining a desired temperature of the fluid are located at at least one location exterior of the mannequin. The desired temperature is preferably similar to that of the skin of the mammalian body being simulated.
Throughout the present application, the word fluid is not intended as a limitation, and is used to signify any medium that satisfies a requirement for heat transfer as well as allowing the system to maintain constant pressure, including fluids such as water, gases such as nitrogen, mixtures of gases such as air, or combinations or suspensions such as fine particulates in air.
The system for measuring a thermal property of a garment comprises a mannequin as above. Means are provided for circulating a fluid through at least a portion of the mannequin, for controlling a temperature of the fluid being circulated for simulating a skin temperature of the mammalian body, for sensing a temperature at at least one location exterior of the mannequin beneath the garment, and for monitoring an energy usage required to control the fluid temperature. The energy usage is indicative of the thermal property of the garment.
A method for measuring a thermal property of a garment comprises the steps of placing a mannequin as above in a desired environment and channeling a fluid through at least a portion of the mannequin and establishing a control value. Next a garment for which it is desired to have a thermal property measured is placed onto the mannequin, and a change in the electrical energy is determined.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.